The state of a transmission path in wireless communication performed in an on-board wireless communication apparatus momentarily fluctuates, and the fluctuation becomes further noticeable as the on-board wireless communication apparatus moves. Patent Document 1 discloses a portable communication terminal apparatus capable of reducing power consumption while reducing the consumption of a communication resource even when the state of the transmission path is unstable. In the portable communication terminal apparatus, as an acceleration or moving speed thereof is increased, a packet error rate is increased, so that the packet error becomes likely to occur, and thus an object of the apparatus is to avoid the packet error by changing a transmission rate and avoid/reduce unnecessary consumption of the communication resource by retransmission; it is schemed that a packet length is changed in accordance with the acceleration or moving speed.